reduction of sound with low frequency by fractal objects

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We surround with various kind of sounds. Among such sounds, it is a pressing issue to reduce the low-frequency noise because of its endangering our health. The aim of our research is to investigate a possibility to reduce such sounds by means of fractal objects. Specifically, we have systematically studied sound properties of several fractal objects such as Koch curve, Sierpinski carpet, Menger sponge from theoretical, numerical and experimental viewpoints. Especially, we have shown that the transmission loss by fractal surface increases with the fractal order. Furthermore, the range of frequency effective with sound absorption widens and the peak of frequency shifts toward lower values of frequency with the fractal order. These results strongly indicate that fractal nature of self-similarity is responsible for the reduction of low-frequency sounds and that there is possibility of practical application of fractal objects to lowering low-frequency noise.